400291 signup issue 2

Hello, I think I have a bug on my signup page here [login to view URL]*[login to view URL] delete the * There is sometimes a problem creating a signup. Sometimes it gives an error of "Error Please enter your User name" I need this to work on IE,FF,and Opera without a problem. Would be great if it also worked on the mac version of FF and IE. It worked for me on FF 3.5.8 on my pc..but for my friend for FF 3.5.8 it didnt work.